Much industrial effort has been devoted to developing ground-engaging tools with a reduced cost to wear-life ratio. For example, new material compositions and heat treatments have been responsible for lowering the wear rates of cutting edges for earthmoving blades and the tips for penetrating teeth. Moreover, various hardfacing materials have been weldingly applied to the exposed wear surfaces of such tools; but unfortunately, these thin hard facings wear away relatively quickly and it is necessary to apply additional layers at considerable expense.
Particularly promising are those activities relating to the use of composite wear-resistant materials which embody a plurality of highly abrasive-resistant particles in a tough carrying matrix material. These composite materials are typically deposited on the tool or are made into inserts. Illustrative thereof are U.S. Pat. No. 3,757,879 issued Sept. 11, 1973 to A. G. Wilder et al., and U.S. Pat. No. 3,800,891 issued Apr. 2, 1974 to A. D. White et al.
In addition to economic considerations, these composite materials must be located in optimum locations on the tool because they tend to crack off or fail by spalling under the severe working conditions so frequently encountered. Representative of the diverse efforts to situate wear-resistant members, composite or otherwise, in an optimum location relative to the normal direction of tool travel, are the following U.S. Pat. Nos.:
1,583,701 issued May 4, 1926 to O. A. K. Printz PA1 1,965,950 issued July 10, 1934 to C. M. Walker PA1 2,033,594 issued Mar. 10, 1936 to S. M. Stoody PA1 2,549,088 issued Apr. 17, 1951 to H. C. Hettelsater et al. PA1 3,529,677 issued Sept. 22, 1970 to E. W. Stephenson PA1 3,888,027 issued June 10, 1975 to L. F. Toews